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SCIENCE- G OS SIP. 



by John Cuff. The date of its introduction was 

 1 744, and it was called " A New Constructed 

 Double Microscope." After the John Marshall 

 microscope this is, historically, one of the most 

 important instruments in the Society's collection. 

 The other microscope presented was made by 

 Plossl & Cie.,Wien, and has already been described 

 in the Journal of the Society. Messrs. R, & J. 

 Beck exhibited a new pattern microscope embody- 

 ing several new features. The sub-stage was fitted 

 with coarse and fine adjustments, and means of 

 throwing out the condenser while it was in focus. 

 The stage, 5 in. diameter, was rotating, and gradu- 

 ated on the periphery, with a removable mechani- 

 cal stage graduated as a finder. The body was 

 very short, fitted with a double draw-tube, which 

 allowed the body to be extended to llf-in. The 

 body was fitted with Ashe's new double fine ad- 

 justment. Mr. Conrad Beck gave an exhibition 

 of antipoints, and said they were extremely diffi- 

 cult to show on account of the trouble there was 

 in obtaining points of light sufficiently small 

 and bright, and it was only possible to obtain 

 faint images wdth so much diffused light as there 

 was in that room. There were six microscopes, all 

 having ^-in. objectives, and the points of light 

 in the first two cases were produced by minute 

 apertures in tinfoil ; in the others the light was re- 

 flected from small mercury globules. With the 

 first microscope a point of light w T as viewed with 

 J-in. objective of ordinary aperture, and showed 

 a point of light surrounded with faint diffrac- 

 tion circles. With the second microscope a simi- 

 lar point of light was viewed with a J-in. objec- 

 tive of very small aperture, and showed a disc of 

 light and diffraction rings. The other microscopes 

 showed the effects produced by placing various 

 stops behind the objectives, and also by viewing 

 the point of light through a grating which ex- 

 tended the whole aperture of the objective. 

 Mr. J. W. Gordon said he had listened with great 

 interest to Mr. Beck's explanation of the demon- 

 stration and was anxious to see the examples, and 

 no doubt the experiments would demonstrate the 

 existence and appearance of the antipoint in each 

 case, but there was another and equally important 

 image which he would like to see, and that was 

 the antipoint which was formed in the eye, and 

 he hoped some day Mr. Beck would be able to 

 give a demonstration of this. A paper " On Stereo- 

 micrography," by Professor G. P. Girdwood, of 

 M'Gill College, Montreal, was read by the Secretary. 

 Professor Girdwood's method of obtaining stereo- 

 microphotographs was by placing the slide or object 

 in a tilting frame attached to the stage of the micro- 

 scope. The frame with the object was tilted to 

 one side to the proper angle and a photograph was 

 taken ; the frame was then tilted to an equal 

 amount in the opposite direction and another 

 photograph was taken. Prints from the negatives 

 were then mounted in the usual way to form 

 stereoscopic pictures. The paper was illustrated 

 by a diagram on the blackboard, and a specimen 

 of the stereoscopic photographs placed in a stereo- 

 scope was passed round the room. 



Quekett Microscopical Club. — The 390th 

 ordinary meeting was held on November 15th at 

 2') Hanover Square, W., Mr. J. G. Waller, F.S.A., 

 vice-president, in the chair. — Additions to I he 

 library and cabinet were announced. A paper by 

 Mr. A. A. Merlin, on the " Spermatozoon of the 

 Rat," was taken as read. The Secretary read a 



paper, also by Mr. Merlin, " On the Critical Employ- 

 ment of the Microscope for Ordinary Working 

 Purposes." The author enumerated and considered 

 the causes of indifference and opposition to the 

 employment of " critical " methods in the general 

 use of the microscope. The importance of the 

 wide axial cone of illumination with all powers 

 was insisted upon: and, although the author 

 deplored the absence from opticians' catalogues of 

 good low-power achromatic condensers, yet he 

 showed how this want could be met by means 

 nearly as efficient. A few simple experiments were 

 recommended, to convince the naturalist or other 

 low-power worker of the advantage and necessity 

 of relatively wide cones from a condenser with 

 low-power objectives. The author also dealt with 

 the corrections of the objective, which depended 

 upon thickness of cover-glass, and the necessity of 

 adjusting the correction-collar or tube-length to 

 obtain good results. Preservation of the eyes and 

 increase in their perception could be assisted by 

 working in a darkened room and by occasional 

 rests in the dark for a few minutes. Too intense 

 illumination was to be avoided by the use of such 

 screens as the copper acetate solution, and not by 

 modifying the cone. The paper also contained 

 useful hints on eyepieces, etc. In the succeeding 

 discussion Mr. W. B. Stokes said that the remarks 

 they had just heard might be of use, not only to 

 the younger members to whom they w-ere addressed. 

 but also to many who had worked for years with 

 the microscope. He instanced the apathy with 

 regard to "critical" methods frequently noticeable 

 in that room. He had seen objectives corrected 

 for the short tube used on a long body, though 

 correction for thickness of cover-glass was impos- 

 sible under such conditions. The same objective 

 might require a 4-inch tube with a thick cover- 

 glass, while with a thin cover a 15-inch tube might 

 be necessary before fine detail was shown clearly. 

 Such variations of tube-length were not practicable 

 on most microscopes. His own experience was 

 short and his work intermittent, but he could 

 endorse Mr. Merlin's remarks on the advantages of 

 a darkened room and occasional rests in the dark. 

 Several objects were exhibited after the formal 

 proceedings terminated. 



Manchester Microscopical Society. — At the 

 monthly meeting of this Society held at the Grand 

 Hotel, Manchester, on December 5th, Prof. Sydney 

 J. Hickson, M.A., D.Sc, F.R.S., delivered his Presi- 

 dential Address on the subject of Fertilisation. 

 He said that modern researches have cleared away 

 a great many false hypotheses as to the nature of 

 fertilisation, and had thrown much light on the 

 biological meaning of the process. The study of 

 the Protozoa had conclusively proved that the 

 germinal cells were originally equal in bulk as well 

 as being equivalent in function. The differentia- 

 tion into ova and spermatozoa is characteristic of 

 the Metazoa, and is accounted for by the necessity 

 of the young embryo to have a sufficient supply of 

 food material. After a discussion on the fusion 

 of all parts of the germinal cells in fertilisation, 

 the President proceeded to describe the recent 

 experiments on artificial parthenogenesis, and 

 pointed out the bearing of these facts on the 

 theories of fertilisation. The address was illus- 

 trated by means of the oxy-hydrogen lantern, 

 many interesting photo-micrographs of the actual 

 fertilisation of the ovum by the spermatozoa 

 beino- shown. 



